Could you be a bit more clear in the question? Do you want to know how to actually write a database system? Or how to design a good schema? Or how to write clas

Could you be a bit more clear in the question? Do you want to know how to actually write a database system? Or how to design a good schema? Or how to write classes that implement a schema for you using a framework? Or something else? In any case there are books on these topics. And there’s open source software that probably does something similar or close to what you want to do. Look at its code and learn from it.